The present invention relates to fluid flow/pressure control and more particularly to methods, apparatuses and devices concerning the automatic relief of an excess negative pressure condition within an apparatus, vessel, medical device or other fluid container.
As is known to those skilled in the medical arts, a number of situations can arise in which it is medical necessary to provide a drain from the pleural cavity. In these cases the pleural cavity is disrupted because of, for example, a blunt trauma injury (e.g., knife wound, gunshot wound, severe automobile accidents) and intentional chest trauma, for examples such as that resulting from thoracic surgical procedures requiring the drainage of air and/or fluid from collecting in the pleural cavity. Other pleural abnormalities include pleural effusion and empyema.
In addition, after heart surgery there is the possibility of the accumulation of blood and clots, for example, in the mediastinum, specifically in the pericardial sac, which can be life threatening. Thus, a drain can be provided for mediastinal drainage to minimize the risk of cardiac tamponade.
Initially and traditionally, such chest drainage was accomplished using what has been commonly referred to as a three-bottle chest drainage system. Since then, a number of devices have been developed to mimic the three-bottle system, which devices are sometimes referred to simply as chest drainage units. Such chest drainage units include a mechanism for collecting the liquid effluent from the patient, a patient seal that acts as a one-way valve so as to allow gaseous effluent to leave the pleural cavity but prevents a gas such as air from returning to the pleural cavity and a mechanism for limiting or controlling the amount of suction that can be applied to the pleural cavity by the chest drainage unit. A line(s) also is typically provided to connect the chest drainage unit to the pleural cavity and/or the mediastinum so that fluids can be withdrawn therefrom and collected in the chest drainage unit. In addition, another portion of the chest drainage unit is connected to a negative pressure source or vacuum/suction source, so as to cause the fluid or liquid effluent to flow to the drainage device and, in the case of the pleural cavity also maintaining a negative pressure in the pleural cavity so as not to compromise the full expansion of the lung.
It is possible to develop high or excess negative pressure conditions within such chest drainage units that must be relieved so as to avoid or minimize the risk of damage to tissue surrounding the drainage tube within the patient""s body. Thus, specific measures or mechanisms are put into place so that such high or excess negative pressure conditions (i.e., a more negative pressure condition) can be removed and so that normal negative operational conditions can be re-established within the chest drainage unit.
Such high negative pressure conditions can result from a number of circumstances including, for example, patient coughing or medical personnel milking or stripping of the drainage tubing so as to cause any clots or the like to move towards the chest drainage unit. Milking is a term that is generally used to describe gentle kneading of short sections of the tubing so as to cause momentary burts of suction within the tubing. Stripping is a much more vigorous procedure during which long lengths of the tubing are compressed and released. Stripping can cause dangerously high negative pressures.
Initially, one form of protection from high or excess negative pressure condition was a manually actuated valve whereby the medical personnel would depress or push a button of the manually actuated valve so as to allow external air to be introduced into the chest drainage unit, thereby alleviating the high negative pressure condition. For this form of protection to work, however, the medical personnel must first observe the patient and determine that a high negative pressure condition exists before they would actuate the manual valve. Thus, it may take some time after the onset of the high or excess negative pressure condition before such a condition is detected by the medical personnel and rectified by manual actuation of the relief valve.
Some recent chest drainage units, particularly those units that embody a dry suction type of control mechanism, for example that shown in U.S. Pat. No. 5,989,234, have included an automatic high-pressure negative pressure relief valve alone or in combination with a manually actuated relief valve. The automatic pressure relief valve is configured so it automatically opens and closes responsive to the negative pressure conditions within the chest drainage unit. Further, such an automatic relief valve typically is configured to open when a predetermined negative pressure condition or an even more negative condition is established within the collection chamber or section of the chest drainage unit, which pressure condition is in excess (i.e., more negative) of any of the normal operating suction or negative pressure conditions that can be developed in the collection chamber or section. For example, in some chest drainage units with a dry suction control regulation device designed to maintain suction pressures up to and including xe2x88x9240 cm of water, the set point for the automatic negative pressure relief valve is about xe2x88x9250 cm of water.
One such automatic high or excessive negative pressure relief valve is the adjustable check valve found in U.S. Pat. No. 4,550,749. Material properties of the resilient valve element of this pressure relief valve, such as the rigidity of the material, dictates at what pressure and where the resilient valve element will reseal. Consequently, this valve does not close as accurately as is desired. In addition, it has been observed that the pressure differential for closure varies from valve to valve. This failure to close accurately necessarily means that more air is being admitted into the chest drainage unit than is needed to overcome the high negative pressure condition. As such, the excess air needs to be withdrawn from within the chest drainage unit in order to restore normal operational negative pressure conditions. In addition, it has been observed that this adjustable check valve has proven to be difficult to manufacture.
There is found in U.S. Pat. No. 6,024,120 another negative pressure relief valve for relieving an excess negative pressure condition, that is configured so as to function either automatically or manually. In this valve, a diaphragm is slidably moved along a length of a piston rod. One end of the piston rod is configured so as to have a plurality or more of leg like members with a void between each leg. Thus, when the diaphragm slides over the leg like members, the suction side of the valve is put into fluid communication with the atmospheric side of the valve such that air flows into the chest drainage unit.
In this valve a seal must be maintained between the diaphragm and the exterior surface of the piston rod when the diaphragm is stationary and as it moves along the length of the piston rod until the suction side of the valve is put into fluid communication with the atmospheric side of the valve. If the seal is not maintained, the relief valve will leak air into the collection chamber or collection section side of the chest drainage unit. It is possible that the medical personnel could initially misinterpret such an air leak as being representative of the presence of an air leak upstream of the chest drainage, for example in the interconnecting tubing or at the drainage site (i.e., patient). In order to establish such a seal, the diaphragm must exert a radial force urging the inner periphery of the diaphragm into sealing engagement with the exterior surface of the piston rod. Because this force necessarily retards the motion of the diaphragm, it impacts the set point of the relief valve.
It thus would be desirable to provide a new automatic excess or high negative pressure relief valve that would respond to the negative pressure differentials typically seen in chest drainage units as well as chest drainage units and methods related thereto. It would be particularly desirable to provide such a pressure relief valve and related method that would more consistently open and close at the desired negative pressure conditions in comparison to prior art pressure relief valves/devices. It also would be desirable to provide such a pressure relief valve that is easily adjusted to any one of a number of negative pressure set points or within a range of negative pressures as compared to prior art pressure relief valves/devices. Such pressure relief valves preferably would be simple in construction, and less costly than prior art valves and such methods would not require highly skilled users to utilize the valves/device.
The present invention features an automatic high or excess negative pressure relief valve and methods related thereto. Such an automatic high or excess negative pressure relief valve when used in a chest drainage unit provides a mechanism to relieve excessively high negative pressure levels in that portion of the chest drainage unit in which liquid effluent from the patient is being collected, hereinafter generally referred to as the collection chamber. Also featured is such a high or excess negative pressure relief valve used in combination with any of a number of chest drainage units known to those skilled in the art, more particularly, chest drainage units characterized as having either wet or dry suction control and/or a wet or dry patient seal.
In its broadest aspects, such an automatic high or excess negative pressure relief valve includes a biasing mechanism that acts on a moveable member such that when the negative pressure level within a chamber, in which a portion of the relief valve is in fluid communication with, is less than a predetermined negative pressure value (i.e., less negative pressure condition) the moveable member is moved into sealing engagement with a sealing surface. When the negative pressure levels within this chamber are at or above the predetermined value (i.e., a larger or more negative pressure condition), the restoring force of the biasing mechanism is overcome and the moveable member moves away from the sealing surface, whereby air or other gaseous material is admitted into the chamber via the an automatic high or excess negative pressure relief valve.
In a more particular embodiment, the biasing mechanism is a spring member that acts on the moveable member, which spring member is configured and arranged so as to develop a force on the moveable member so as to have the above-described effect. It should be recognize that the biasing mechanism can be any of a number of mechanisms known to those skilled in the art that produces the above described biasing effect on the moveable member, including those that can be adapted for use in the present invention. As illustrative embodiments, such other biasing mechanisms include, but are not limited to a wave washer, diaphragm, leaf spring, hydraulic member, or pneumatic piston.
In another embodiment, the automatic high or excess negative pressure relief valve includes at least one first port in fluid communication with a gas source such as atmosphere and at least one second port in fluid communication with the chamber. In addition, the moveable member and the sealing surface are arranged so as to be disposed between the first port and the second port and so that when the moveable member is moved away from the sealing surface, the first and second ports are in fluid communication with each other, whereby gas from the gas source flows into the chamber.
According to one aspect of the present invention, the automatic high negative pressure relief valve includes a housing, a biasing mechanism, a sealing member moveable disposed within the housing, a flexible member and a seating surface. The flexible member is configured and arranged so as to extend between an interior of the housing and the sealing member so as to form a first and a second chamber within the housing, where the first chamber is fluidly coupled to a gas source and the second chamber is fluidly coupled to an interior of a vessel such that a pressure level within the second chamber corresponds to a pressure level within the vessel interior.
The biasing mechanism is disposed and arranged within the housing so as to act on the sealing member such that when the pressure level within the second chamber is less than a predetermined value (i.e., a less negative pressure condition) the sealing member is moved into sealing engagement with the seating surface. When the pressure level within the second chamber is at or above the predetermined value (i.e., a higher or more negative pressure condition), the restoring force of the biasing mechanism is overcome and the sealing member moves away from the seating surface, whereby gaseous material is admitted into the interior of the vessel via the an automatic high or excess negative pressure relief valve.
In a particular embodiment, the biasing mechanism comprises a spring, more specifically a spring under compression. The spring is configured and arranged so as to generate a force sufficient in magnitude to put the sealing member in sealing engagement with the seating surface when a differential pressure between the first and second chambers is less than a predetermined differential pressure value. The spring also is configured and arranged so the force that can be generated by the spring will allow the sealing member to move away from or be spaced from the seating surface when a differential pressure between the first and second chambers is at or above the predetermined differential pressure value. Stated another way, the spring force is established such that the sealing member is not prevented from moving away from or being spaced from the seating surface when a differential pressure between the first and second chambers is at or above the predetermined differential pressure value. As indicated hereinabove, the biasing mechanism is not limited to this particular embodiment as other biasing mechanism known to those skilled in the art are contemplated for use with the present invention.
The flexible member is configured (e.g., made of a material) so it essentially does not impose a force on the sealing member as the sealing member moves responsive to the biasing mechanism and differential pressure conditions. In particular embodiments, the flexible member is configured so it essentially does not impose a changing force on the sealing member as the sealing member moves responsive to the biasing mechanism and differential pressure or so that motion of the sealing member responsive to the biasing mechanism and differential pressures is essentially frictionless. More particularly, the flexible member is configured so it does not have, in effect, a spring rate that opposes motion of the sealing member responsive to the biasing mechanism and differential pressures. In this way, the spring force essentially establishes the opening and closing points of the automatic high negative pressure relief valve of the present invention. In an exemplary embodiment, the flexible member is a thin soft elastomer material.
In a further embodiment, the automatic high negative pressure relief valve includes a seating surface member that is configured and arranged to provide the seating surface for a portion of the sealing member, more particularly to provide a seating surface that sealingly engages a portion of a surface of the sealing member. In a particular embodiment, the seating surface member is configured and arranged to establish a seal between the seating surface member and the sealing member while minimizing the contact surface area therebetween. In a more particular embodiment, the seating surface member is conical in shape. More specifically, the conical seating surface member is configured and arranged so a portion of the exterior surface of the conical seating surface member sealingly engages the portion of the surface of the sealing member.
In more particular embodiments, the sealing member is configured so as to include a through aperture in the portion of the surface of the sealing member. In this embodiment, the exterior surface of the conical seating surface member sealingly engages interior portions of the through aperture. In a more specific embodiment, the exterior surfaces of the conical seating surface member are in edge or line contact with an interior edge of the through aperture.
In even a more particular embodiment, the sealing member is configured and arranged so as to include an extension member that extends outwardly from the surface of the sealing member. The extension member includes the through aperture, interior portions of which sealingly engage the exterior surface of the conical seating surface member. In an exemplary embodiment, the extension member is a tubular member. In a more specific embodiment, the exterior surfaces of the conical seating surface member are in edge or line contact with an interior edge of the through aperture of the extension member.
In an exemplary embodiment, the housing includes a cover member and a base. The cover member includes at least one, more particularly a plurality, more specifically a multiplicity of through apertures therein, the cover through apertures providing a fluid flowpath between the vessel interior and the second compartment. The base is configured and arranged so as to include at least one, more particularly a plurality, more specifically a multiplicity of through apertures or channels therein, where the through apertures or channels provide a fluid flowpath between the gas source and the first compartment. In a more particular embodiment, the base is configured and arranged so as to include the above-described seating surface member. In a more specific embodiment, the one or more apertures are arranged so as to be about and proximal the conically shaped seating surface member.
According to a second aspect of the present invention, the automatic high negative pressure relief valve includes a housing, a biasing mechanism, and a sealing member moveable disposed within a chamber in the housing. The housing is configured and arranged so that a surface of the chamber comprises a seating surface, a first through aperture is provided in the seating surface which aperture is in fluid communication with a gas source, such as atmosphere, and at least one, more particularly a plurality of second through apertures one end of each being fluidly coupled to the housing chamber and another ends of each being fluidly coupled to the interior of a vessel.
The biasing mechanism is disposed and arranged within the housing chamber so as to act on the sealing member such that when the pressure level within the one or more second through apertures is less than a predetermined value (i.e., a less negative pressure condition) the sealing member is moved into sealing engagement with the seating surface. When the pressure levels within the one or more second through apertures are at or above the predetermined value (i.e., a higher or more negative pressure condition), the restoring force of the biasing mechanism is overcome and the sealing member moves away from or is spaced from the seating surface, whereby gaseous material is admitted into the interior of the vessel via the an automatic high or excess negative pressure relief valve.
In a particular embodiment, the biasing mechanism comprises a spring, more specifically a spring under compression. The spring is configured and arranged so as to generate a force sufficient in magnitude to put the sealing member in sealing engagement with the seating surface when a differential pressure between the chamber and the first through aperture is less than a predetermined differential pressure value. The spring also is configured and arranged so the force that can be generated will allow the sealing member to move away from or be spaced from the seating surface when a differential pressure between the chamber and the first through aperture is at or above the predetermined differential pressure value. Stated another way, the spring force is such that it will not prevent the sealing member from moving away from the seating surface when a differential pressure between the chamber and the first through aperture is at or above the predetermined differential pressure value. In an exemplary embodiment, the sealing member includes an aperture in which is received the spring or biasing mechanism.
According to a third aspect of the present invention, an automatic high-negative pressure relief valve, including those described hereinabove, is configured and arranged so as to include a mechanism for selectively adjusting the biasing mechanism so as to selectively adjust the force being applied to or acting on the sealing member by the biasing mechanism. In this way, one can in adjust the set point of the relief valve (i.e., when the valve will open). In the case where the biasing mechanism comprises a spring, the adjusting mechanism selectively compresses and decompresses the spring, thereby adjusting the spring force being applied to sealing member.
In an illustrative embodiment, the adjusting mechanism is threadably disposed within a threaded aperture in the housing such that rotation of the adjusting mechanism in one of a counter-clockwise or clockwise direction causes the biasing mechanism to be adjusted so as to increase or decrease the force being applied to the sealing member. In an illustrative exemplary embodiment, the adjusting mechanism is a threaded member, one end of which is configured and arranged so as to engage an end of the spring comprising the biasing mechanism such that the spring is selectively compressed or de-compressed responsive to the direction of rotation and the amount of rotation of the threaded member. In further specific embodiments, the adjusting mechanism and the housing cooperate so that the adjusting mechanism is sealing disposed within the housing.
According to fourth aspect of the present invention, an automatic high-negative pressure relief valve, including those described hereinabove is configured and arranged so as to include a filtering mechanism being configured and arranged to filter incoming gas (e.g., air) from the gas source (e.g., atmosphere) prior to it flowing into the interior of the vessel such as the collection chamber of a chest drainage unit. In an exemplary embodiment, the filtering mechanism comprises any of a number of filtering mediums known to those skilled in the art by which the gas from the gas source is filtered to a desired state/condition before being passed to the vessel interior.
Other aspects and embodiments of the invention are discussed below.